Shield pole perpendicular magnetic recording (PMR) writers are commonly used in current PMR (hard disk drive) HDD products. PMR writers have become the mainstream technology for disk drive applications beyond 200 Gbit/in2, replacing longitudinal magnetic recording (LMR) devices. Due to the continuing reduction of transducer size, high moment soft magnetic thin films with a Bs above 22 kG are required for write head applications. A PMR head combines the features of a single pole writer and a soft magnetic underlayer to offer a great advantage over LMR in providing higher write field, better read back signal, and potentially much higher areal density. In particular, a shielded pole head can provide a large head field gradient at the trailing side due to the presence of a trailing shield and substantially improve the write performance.
Referring to FIG. 1a, a prior art shield pole PMR writer 1 is depicted from a side-track view. There is an essentially flat write gap layer 4 which separates a main pole layer 3 and a trailing shield 5 by a constant (WG) thickness. One end of the main pole layer is formed along an air bearing surface 6 that is positioned above a magnetic recording medium 2. The height of the trailing shield also known as throat height (TH) is the distance from the side of the trailing shield along the ABS to the side opposite the ABS and is typically about 0.1 to 0.3 microns. The PMR writer moves along the ABS in a negative z direction during a write operation. From a down-track perspective in FIG. 1b, the main pole layer 3 is comprised of a write pole 3a that terminates in a pole tip 3t at the ABS 6-6, and a yoke 3b that flares outward at an angle θ from the end of the write pole opposite the ABS. The end of the write pole 3a lies along the plane 7-7 that is a neck height (NH) distance from the ABS. The intersection of the yoke 3b and write pole 3a is at the neck 8. In order to optimize both write field gradient and write field magnitude, TH (FIG. 1a) is preferably short. However, in prior art PMR writer structures, a short TH can be very challenging to control during the fabrication process. Furthermore, if the TH becomes too small, saturation of the trailing shield and degradation of the signal-to-noise ratio (SNR) may occur. Therefore, an improved PMR writer design is desired that is more tolerant of short TH dimensions and enables improved writability while minimizing trailing shield saturation and avoiding loss of process control during fabrication.
A routine search of the prior art revealed the following references. In U.S. Patent Application Publication No. 2005/0219743, a single pole vertical write head is described having a trailing shield tapered to the same angle as the main pole with a constant write gap thickness between the trailing shield and main pole.
In U.S. Patent Application Publication No. 2005/0237665, the main pole is tapered at the leading side to maintain high trailing field gradients and is shielded on four sides to minimize adjacent track erasure.
U.S. Patent Application Publication No. 2006/0203395 discloses a perpendicular recording head with a tapered magnetic shield to minimize stray fields at the recording surface. The ABS is post-lapped using an ion milling process to produce a recess in the shield away from the ABS at a shallow angle.
In U.S. Pat. No. 5,600,519, first and second magnetic layers in a magnetic head are progressively widened (tapered) between a zero throat point and a flare point so that the length of the magnetic yoke layers between the aforementioned points is saturated nearly simultaneously to provide a constant write field about a saturation value.
U.S. Pat. No. 5,173,821 discloses a write/read head wherein a stepped pole tip effectively forms a wide gap when the head operates as a recording head and forms a narrow gap when the head functions as a read head.